Cartridges used with firearms can be either the center-fire type or the rim-fire type, depending on the position of the "primer" in the cartridge. Typically, problems can be incurred when loading or unloading such cartridges into the associated magazine. Particularly when rim-fired cartridges are used, loading and unloading difficulties can arise as rim-fired cartridges have a rim section of greater diameter than the diameter of the main body portion of the cartridges.
In the past, such cartridges have been inserted into the magazine against the bias of a spring biassed follower; that is, when manual force is applied to a cartridge to insert it into the magazine, it was required that force be sufficient to oppose the bias of a follower. In magazines, the follower is the movable portion which exerts an upward force on the lowermost cartridge in the magazine. The follower is typically spring biased to exert such upward force. The forcing of the cartridges into the magazine against a bias has in the past resulted in damage to the cartridges. Also, jamming of the cartridges, particularly in the case of rim-fired cartridges, can easily result. Also, if the user is not forceful and careful, a rebound effect can occur because of the strong force of the biased follower. Thus, in loading, several cartridges can rebound or spring back out of the magazine. Also, proper alignment of the cartridges can be difficult when the user is attempting to overcome the bias of the follower by pushing on the cartridge to be inserted.
In unloading magazines with biased followers, the user generally pries each cartridge out of the magazine. As in loading, several cartridges may eject out of the magazine at once. The force of the biased follower will cause the ejection of the cartridges to be in an uncontrolled manner. Alternatively, in the past a user, on occasion, inverted the magazine to shake any unused cartridges free. Again, such an unloading method lacks control, and can result in damage and scattering of the cartridges.